The invention relates to an optical system comprising a polarizing element in the form of a layer comprising an isotropic material having a refractive index ni, and an anisotropic material having refractive indices n.sub.a,e and n.sub.a,o, in which n.sub.i is substantially equal to n.sub.a,e or n.sub.a,o.
The invention also relates to a flat picture display device and to an image projection device provided with such an optical system.
A polarizing element as described in the optical system of the type described in the opening paragraph is known from, for example the publication: "Polarizer" in Research Disclosure, July 1993, no. 35117, pp. 452-453.
The polarizer described in this publication comprises a layer of birefringent material which is present between two glass plates and in which glass granules are distributed. The glass granules have a refractive index which is equal to the ordinary refractive index of the birefringent material. Consequently, an unpolarized light beam incident on the polarizer will fall apart into an ordinary and an extraordinary beam component. Since the glass granules have a refractive index which is equal to the ordinary refractive index of the birefringent material, the ordinary beam component will be passed, whereas the extraordinary beam component will be diffused in the layer and consequently disappears from the light path.
A drawback of such a polarizer is that substantially half the intensity of an incident light beam is lost because the beam component having the unwanted direction of polarization is removed from the light path.